This invention relates to crawler shoes used in crawler tracks for mining shovels or other heavy-duty equipment.
Electric mining shovels use an endless belt of crawler shoes to both distribute the weight of the machine on the ground and to transverse uneven ground conditions. Each shoe must be capable of supporting up to one half of the weight of the machine. The crawler shoes are subjected to wear and tear resulting from operation in dust, mud, rock and highly abrasive soils, shock loads, and other severe operating conditions. Adjacent shoes in a crawler track are connected to one another by means of removable, replaceable pins that permit articulation of adjacent shoes and also enable the shoes to be replaced as they become worn. Such crawler shoes are relatively large, being on the order of seven feet wide, for example, and heretofore have been made by casting steel. In a typical crawler track, heavy-duty forged or cast steel rollers ride upon the upper surface of each shoe and transfer crushing loads thereto from the heavy machinery there above. The load is transferred from lower rollers and idlers on the shovel to the roller path of the shoe. The roller path of the shoe is subjected to high contact stresses in the contact zone of the rollers.
Crawler shoes made of manganese steel possess a unique combination of very good toughness and hardness. A manganese shoe is soft, i.e., it has low tensile strength when new. As the roller path is subjected to high compressive stress above the yield strength, the material deforms or flows. The metal flow changes the grain size and shape and effectively work hardens the material. Typically the roller path of a shoe starts out at 200 BHN (Brinell hardness) when new and then work hardens to 500 BHN or more in service. Metal flowed material is plastically deformed and displaced. The majority of the flow and work hardening occurs near the surface of the roller path and the hardening effects diminish with increasing depth in the section of the shoe. The majority of metal flow occurs at early hours of the shoes life. The rate of metal flow decreases significantly as the material on the surface work hardens.
As illustrated in FIG. 1, the prior art shoes 100 have included peening groves 104 in order to allow the manganese steel to flow into them. The peening groves are parallel groves that extend in the direction of the roller path 108, thus allowing the material to work harden without producing undesirable metal flow into other functional areas of the shoe. In other shoes (not shown), half of the roller path had peening grooves angled at about 45 degrees in one direction to the direction of the path of the roller, and the other half of the roller path had peening groves angled at about 45 degrees in the opposite direction to the direction of the path of the roller.